磷浓度对盐生杜氏藻和纤细角毛藻叶绿素荧光特性及生长的影响

在温度(23±1)℃,盐度31,光照度5000 lx的条件下,用含有不同磷浓度(0、2.27、18.15、36.3、72.6、290.4μmol/L)的培养基对盐生杜氏藻和纤细角毛藻进行培养,研究2种微藻在一次性培养过程中,不同磷浓度对其PSII最大光能转化效率(Fv/Fm)、叶绿素含量以及细胞密度的影响。单因子方差分析结果表明,在整个培养周期中,磷浓度对两种微藻的光合作用及生长均有显著影响(P<0.05)。盐生杜氏藻的PSII最大光能转化效率、叶绿素含量以及细胞密度均随着起始磷浓度的增加而增加,在290.4μmol/L处达到最大值;纤细角毛藻的PSII最大光能转化效率、叶绿素含量以及细胞密度在18.15μmol/L处达到最大值,而后随着磷浓度的继续升高,其上述指标反而降低。所以盐生杜氏藻和纤细角毛藻进行光合作用和生长的最适磷浓度分别为290.4μmol/L和18.15μmol/L。     

Mass production of microalgae in six commercial shrimp hatcheries of the Mexican northwest

A 2-year survey in six commercial shrimp hatcheries of the states of Sonora and Sinaloa, in the Mexican northwest, aiming to investigate the variability of the outdoor biomass production and composition of microalgae showed wide differences in daily mean yields, from 0.68 to 1.71×10¹² cells m⁻³ and between 23.9 and 73.9 g m⁻³ of dry organic biomass.

These differences were mostly related to the type of culture containers and consequent differences in light penetration. The best yields were in 0.7 m deep polyethylene tanks and the lowest in 1 m deep concrete tanks with a small surface to volume ratio.

Protein, carbohydrate and lipid yields followed the same trends as biomass production and were mostly associated with the design of the culture containers and, in part, with the geographic location of the hatcheries.

Variability was high also within laboratories, and this was related to seasonal climatic differences. In Sonora, cell concentrations were negatively related to temperature, but organic biomass production increased with the increase of this climatic variable, probably because of larger cell sizes. In contrast, the data obtained in Sinaloa showed that cell concentration and organic biomass are directly related to temperature and inversely to light.

Proteins and lipids were negatively related to temperature in Sonora but not in Sinaloa, where high carbohydrates were associated with low temperatures.

Fatty acid profiles were highly variable in all cases and were not associated with the type of culture containers or, with the possible exception of 18C unsaturates, with the geographic location of the laboratories, indicating as probable sources of variability between and within hatcheries either the handling routines or the composition of the growth media.     

Salinity Preference of Two Diatoms and Their Growth Performance in Three Prepared and Two Alternative On-Farm Media Sources

ABSTRACT

Salinity and preferred nutrient composition of Chaetoceros affinis and Skeletonema costatum were tested. Salinity was tested at 12, 16, 23, 28, and 32 ppt. Three compositions of nitrogen (N), phosphorus (P), and potassium (K) and two on-farm low-cost alternative media sources, cow urine (CU) and hatchery waste water (HWW), were tested to find the suitable NPK ratio and to determine the efficacy of the on-farm media respectively. Chaetoceros affinis preferred 23 ppt salinity, while Skeletonema costatum preferred both 28 and 32 ppt. Among the NPK treatments, higher cell density was observed in 4:1:1 followed by 4:2:1 ratios. Significant differences in maximum cell density of both species were observed in the NPK treatments while only S. costatum showed significant difference in CU and HWW.     

Optimization of growth requirements of marine diatom Chaetoceros muelleri using Response Surface Methodology

The marine centric diatom Chaetoceros muelleri has been widely used as live feed in fish and shellfish aquaculture due to its excellent nutritional properties. The growth of microalgae is affected by various nutritional and environmental parameters, and species specific optimization of these parameters is essential for the development of cost‐effective biomass production process. In this study, the growth of C. muelleri, was optimized using response surface methodology (RSM). The variables nitrate, phosphate, silicate, temperature, pH, salinity and agitation speed were initially screened for biomass production in C. muelleri using Plackett–Burman experimental design, and it was found that nitrate, phosphate, silicate, temperature and pH significantly influenced the biomass production. These variables were further optimized by central composite design of RSM for biomass production and nutrient composition, and the medium was re‐constituted accordingly to have 180 mg L^?1 nitrate, 7.5 mg L^?1 phosphate, 30 mg L^?1 silicate, with optimum growth conditions of temperature at 31°C and pH 6.46. At the end of 10 days culture period under the above conditions, biomass, protein, lipid and carbohydrate significantly increased from 0.360 ± 0.01 mg L^?1, 9.41 ± 0.02%, 18.11 ± 0.01%, 0.6 ± 0.02% to 1.16 ± 0.01 mg L^?1, 11.02 ± 0.01%, 19.58 ± 0.01% and 0.77 ± 0.01% respectively. The biomass production of C. muelleri could be increased 3.2‐fold with an improved nutrient profile by modifying the growth factors, the study thus offering an optimized process for biomass production of C. muelleri.     

C/N对牟氏角毛藻生长速率和总脂含量的影响

以牟氏角毛藻为实验材料,研究了1∶1、2∶1、3∶1、4∶1和5∶1等5种不同C/N比值培养液对牟氏角毛藻生长及总脂含量的影响。结果表明,在C/N比值为2∶1时,牟氏角毛藻的相对生长率最高,达到每天1.98,C/N比值为3∶1时,相对生长率最低,为每天1.69;C/N比值为5∶1时,总脂含量百分比达到最高,为31.26%,C/N比值为2∶1时,总脂含量百分比最低,仅为28.39%;C/N比值为2∶1时,总脂日增量最高,达到0.84,C/N比值为3∶1时,总脂日增量最低,仅为0.64;5种C/N比值对牟氏角毛藻不饱和脂肪酸的积累有不同程度的促进作用,C/N比值为5,总不饱和脂肪酸的比例达最高。综合比较表明,C/N比值为2∶1时,最适合牟氏角毛藻的生长及总脂肪积累。     

Experimental evaluation of a composted seaweed extract as microalgal culture media

An organic culture media based on a composted liquid seaweed extract was developed and tested for growth of Chaetoceros muelleri. The extract was evaluated at two concentrations and then compared with two commercial media: Walne and agricultural fertilizer (AF). The concentrations of nitrogen and phosphorous differed between the two commercial media and the seaweed extract; however, growth of Chaetoceros muelleri was similar. The successful culture of Chaetoceros muelleri in composted liquid seaweed extract suggests the feasibility of and potential use for this natural, organic fertilizer in aquaculture. The seaweed extract is simple to obtain and inexpensive.     

Zeolites and diatom growth

Zeolites are widely used in some Asiatic countries, as they are believed to improve water quality and selectively enhance diatom growth through silicon leaching. Culture experiments with the diatom Chaetoceros sp. in medium f, with no silicate, and enriched with two natural and three artificial zeolitic products, showed an enhancement of between 0.2 and 0.6 cell duplications, which cannot be as a result of higher silicate availability because solubility experiments showed that natural zeolites do not leach any silicon, and that the amounts released by the artificial products are too small to improve diatom growth.     

Growth of Artemia franciscana fed Isochrysis sp. and Chaetoceros muelleri during its early life stages

Survival, growth (length and weight), development, proximate composition, and energy content of Artemia franciscana fed for 7 days with Isochrysis sp. (TISO) or with Chaetoceros muelleri (CHGRA) were compared to evaluate the food value of these microalgae. Mean daily survival was not significantly different, and ranged from 86% to 93%. Diet‐related differences in growth were noted from the third day, and mean final dry weights (DWs) were 171 and 327 μg ind^?1 for Artemia fed TISO and CHGRA respectively. Rates of development were different between diets, with a higher developmental index for Artemia fed TISO before day 3, and a higher index for Artemia fed CHGRA for the rest of the experiment. Chemical analysis showed that carbohydrates decreased to approximately 35% of the initial value in Artemia during the first 24 h, after which they remained approximately stable and similar with both diets. In percentage of total DW, lipids and proteins remained close to their respective initial values, but A. franciscana fed TISO had a higher ash content. A major difference between the two microalgae was the higher protein content of TISO, but this did not result in better growth. Of the two, TISO was richer in docosahexaenoic acid, which might explain the initial faster development, but CHGRA was a better source of eicosapentaenoic acid, which is the most probable explanation of the higher food conversion index, specific growth rate, and energy gain of A. franciscana fed this algae.     

Effects of chloramphenicol, erythromycin, and furazolidone on growth of Isochrysis galbana and Chaetoceros gracilis

This study focused on determining the effects of antibiotics on microalgae used as food for scallop larvae. Six different dose levels of chloramphenicol, erythromycin, and furazolidone were added to cultures of Isochrysis galbana and Chaetoceros gracilis. An in vivo experiment was subsequently conducted to determine the effect of chloramphenicol and erythromycin on larval survival of the Pacific calico scallop Argopecten ventricosus in tanks and on the population of its associated bacteria. Results showed that growth of I. galbana was not significantly affected by chloramphenicol or erythromycin at the test doses of 0.5, 1.0, 3.0, 6.0, 9.0, and 12.0 mg/l. C. gracilis was significantly sensitive to erythromycin and chloramphenicol at doses higher than 0.5 and 3.0 mg/l, respectively. Furazolidone inhibited the growth of both I. galbana and C. gracilis at all test doses. Results showed that exposure of scallop larvae to a dose of 6 mg/l chloramphenicol or erythromycin did not significantly affect growth of I. galbana, significantly enhanced survival of the scallop larvae, and inhibited the growth of Vibrio spp. in tanks. This study demonstrated the adverse effect of chloramphenicol, erythromycin and furazolidone on I. galbana and C. gracilis microalgae but the positive effect on survival of the scallop larvae, decreasing associated bacterial population.     

Effects of single and combined microalgae on larval growth, development and survival of the commercial sea cucumber Holothuria spinifera Theel

The results of the study on the suitable algal feed for the mass rearing of holothurian larvae through hatchery system are presented. Auricularia larvae, after 48 h of fertilization, obtained from induced spawning of Holothuria spinifera, were fed with different algae Isochrysis galbana, Nanochloropsis salina, Pavlova lutheri, Tetraselmis chuii and Chaetoceros calcitrans as well as I. galbana+C. calcitrans to ascertain the effect of single and combined microalgal diet. The rate of feeding was 2 × 10⁴ cells larvae^–1 day^–1 for a period of 9–12 days. The growth rate of 59 μm day⁻¹ with 90% and 43 μm day⁻¹ with 100% occurrence of late auricularia in the larvae fed with C. calcitrans alone and I. galbana+C. calcitrans, respectively, indicated that C.calcitrans itself or in combination with I. galbana is the effective feed for the larvae of H. spinifera.